1. Field of the Invention
This invention relates to electrodes to be used in contact with a living body such as the human body, and more particularly to electrodes to be used as grounding pads opposite active surgical electrodes during surgery.
2. Description of the Prior Art
The conventional electrode or "grounding pad" is contacted with the thigh, back or other portions of the human body at a location opposite an active surgical electrode or electro-surgical pencil with blade. An electric current is passed from the active electrode to the grounding pad through the human body to provide a cutting or coagulating action at selected locations.
In the conventional electrode or grounding pad, a gauze containing a physiological saline solution is affixed on a metal plate of lead, stainless steel or the like, having a lead wire extending therefrom. The electrode is contacted with the human body through the gauze. Unfortunately, such conventional construction of the electrode gives rise to various disadvantages. For example, due to poor flexibility of the electrode, contact with the curved surfaces of a human body can become uneven or the saline solution may dry with extended usage, both of which conditions can result in uneven current density over the contact area and the danger of burns. In addition, miniaturization of such an electrode, for application to limited areas, is difficult. Further, problems with sanitization of the electrode can develop.
Another known construction of the conventional electrode or grounding pad, is of a so-called conductive jelly type, wherein a sponge containing conductive jelly is affixed to an inner surface of a sponge-like substrate to form the electrode. Contact with the human body is effected through the conductive jelly, while the sponge-like substrate is affixed to the human body through adhesive material coated on the marginal portion of the inner surface thereof. A lead wire is connected with the sponge containing the conductive jelly. Although an opposed electrode or grounding pad of this type is at least initially relatively well contacted with the human body so that unevenness of electric current density is relatively decreased, there is still a danger of burns being suffered due to uneven contact when the conductive jelly is dried after being used for a long time. In addition, special steps are required for sanitizing the electrode and preventing water evaporation therefrom, such as, enclosing the electrode in a sanitary bag or sak. Such additional procedure adds complication and expense to the production and use of this type of electrode.
In still another known type of electrode or grounding pad, a metal foil of aluminum or the like is directly contacted with the human body, and the metal foil is attached to a substrate of larger size than the foil, and the substrate is affixed to the human body through adhesive material coated on the marginal portion of the inner surface thereof. Unfortunately, electrodes of this type are liable to wrinkle due to poor flexibility of the metal foil. As a result, contact with the human body is not uniform and uneven current distribution results with the danger of burns occurring. Also, this type of electrode is not suitable for surgical operations on children because of its relatively large size.
In a conventional conductive adhesive, metal particles, such as, of copper or silver, are dispersed in a resin, and this adhesive can be applied to a tape. Unfortunately, the specific resistance of such an adhesive is liable to become uneven or unstable, because it is higher than that of the conductive particles contained in the resin and the particles are not surely contacted with the electric conductor. For this reason, when such a conductive adhesive tape is attached to a living body and to the lead wire, a relatively low resistance value cannot be obtained unless the adhesive tape is attached under strong pressure to cause the metal particles to be forcibly exposed on the surface of the adhesive layer to produce good conductivity. Accordingly, when the conventional adhesive is applied as an opposed electrode or grounding pad for an electric-surgical pencil, or the like, there is a danger of causing a concentration of an electric current density if the pressure on the adhesive is weak or uneven.